Class: DBus::PacketMarshaller

Inherits:
Object
  • Object
show all
Defined in:
lib/dbus/marshall.rb

Overview

D-Bus packet marshaller class

Class that handles the conversion (unmarshalling) of Ruby objects to (binary) payload data.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(offset = 0) ⇒ PacketMarshaller

Create a new marshaller, setting the current packet to the empty packet.



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# File 'lib/dbus/marshall.rb', line 252

def initialize(offset = 0)
  @packet = ""
  @offset = offset          # for correct alignment of nested marshallers
end

Instance Attribute Details

#packet ⇒ Object (readonly)

The current or result packet. FIXME: allow access only when marshalling is finished



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# File 'lib/dbus/marshall.rb', line 248

def packet
  @packet
end

Instance Method Details

#align(a) ⇒ Object

Align the buffer with NULL (0) bytes on a byte length of a.



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# File 'lib/dbus/marshall.rb', line 269

def align(a)
  @packet = @packet.ljust(num_align(@offset + @packet.length, a) - @offset, 0.chr)
end

#append(type, val) ⇒ Object

Append a value val to the packet based on its type.



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# File 'lib/dbus/marshall.rb', line 311

def append(type, val)
  type = type.chr if type.kind_of?(Fixnum)
  type = Type::Parser.new(type).parse[0] if type.kind_of?(String)
  case type.sigtype
  when Type::BYTE
    @packet += val.chr
  when Type::UINT32
    align(4)
    @packet += [val].pack("L")
  when Type::UINT64
	align(8)
	@packet += [val].pack("Q")
  when Type::INT64
	align(8)
	@packet += [val].pack("q")
  when Type::INT32
    align(4)
    @packet += [val].pack("l")
  when Type::UINT16
    align(2)
    @packet += [val].pack("S")
  when Type::INT16
    align(2)
    @packet += [val].pack("s")
  when Type::DOUBLE
    align(8)
	@packet += [val].pack("d")
  when Type::BOOLEAN
    align(4)
    if val
      @packet += [1].pack("L")
    else
      @packet += [0].pack("L")
    end
  when Type::OBJECT_PATH
    append_string(val)
  when Type::STRING
    append_string(val)
  when Type::SIGNATURE
    append_signature(val)
  when Type::VARIANT
    if not val.kind_of?(Array)
      raise TypeException
    end
    vartype, vardata = val
    vartype = Type::Parser.new(vartype).parse[0] if vartype.kind_of?(String)
    append_signature(vartype.to_s)
    align(vartype.alignment)
    sub = PacketMarshaller.new(@offset + @packet.length)
    sub.append(vartype, vardata)
    @packet += sub.packet
  when Type::ARRAY
    if val.kind_of?(Hash)
      raise TypeException if type.child.sigtype != Type::DICT_ENTRY
      # Damn ruby rocks here
      val = val.to_a
    end
    if not val.kind_of?(Array)
      raise TypeException
    end
    array(type.child) do
      val.each do |elem|
        append(type.child, elem)
      end
    end
  when Type::STRUCT, Type::DICT_ENTRY
    raise TypeException if not val.kind_of?(Array)
    if type.sigtype == Type::DICT_ENTRY and val.size != 2
      raise TypeException
    end
    struct do
      idx = 0
      while val[idx] != nil
        type.members.each do |subtype|
          raise TypeException if val[idx] == nil
          append(subtype, val[idx])
          idx += 1
        end
      end
    end
  else
    raise NotImplementedError
  end
end

#append_signature(str) ⇒ Object

Append the the signature signature itself to the packet.



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# File 'lib/dbus/marshall.rb', line 280

def append_signature(str)
  @packet += str.length.chr + str + "\0"
end

#append_simple_string(s) ⇒ Object

Append a string of bytes without type.



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# File 'lib/dbus/marshall.rb', line 306

def append_simple_string(s)
  @packet += s + "\0"
end

#append_string(str) ⇒ Object

Append the the string str itself to the packet.



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# File 'lib/dbus/marshall.rb', line 274

def append_string(str)
  align(4)
  @packet += [str.length].pack("L") + str + "\0"
end

#array(type) ⇒ Object

Append the array type type to the packet and allow for appending the child elements.

Raises:



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# File 'lib/dbus/marshall.rb', line 286

def array(type)
  # Thanks to Peter Rullmann for this line
  align(4)
  sizeidx = @packet.size
  @packet += "ABCD"
  align(type.alignment)
  contentidx = @packet.size
  yield
  sz = @packet.size - contentidx
  raise InvalidPacketException if sz > 67108864
  @packet[sizeidx...sizeidx + 4] = [sz].pack("L")
end

#num_align(n, a) ⇒ Object

Round n up to the specified power of two, a



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# File 'lib/dbus/marshall.rb', line 258

def num_align(n, a)
  case a
  when 1, 2, 4, 8
    bits = a - 1
    n + bits & ~bits
  else
    raise "Unsupported alignment"
  end
end

#struct ⇒ Object

Align and allow for appending struct fields.



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# File 'lib/dbus/marshall.rb', line 300

def struct
  align(8)
  yield
end